1. Field of the Invention
This invention relates to airbags and, more particularly, to an airbag door assembly which can be incorporated into the instrument panel of a passenger vehicle. The invention is also directed to a method of making the airbag door assembly.
2. Background Art
There is an increasing trend to incorporate airbags at other than the driver""s location in a moving vehicle so as to protect passengers. A typical airbag system consists of an expandable airbag encased within a housing that is attached to the back of an instrument panel in front of an occupant""s seat. The instrument panel typically has an opening through which the airbag projects as it is expanded upon being deployed. The undeployed airbag within the housing is normally concealed by a door which covers the opening through the instrument panel. Typically, the external surface of the door has an appearance that is matched to the other exposed portions of the instrument panel.
In the event that the vehicle is subjected to a shock, as by that resulting from a collision, the airbag deploys. As the airbag expands, it opens the door over the instrument panel opening and projects therethrough into a deployed state.
Conventionally, the door provided over the instrument panel opening is not integrally formed with the instrument panel. Instead, the door is separately manufactured and joined with the instrument panel. One known process for effecting this combination is known as bi-chromaticforming. Through this process, different resins are used to construct the airbag door and the remainder of the exposed instrument panel.
This conventional structure has some inherent drawbacks. First, by reason of using a separate door element, the door may not visually blend with the remainder of the instrument panel. Thus, the overall appearance of the instrument panel may be compromised. Second, the door and instrument panel may be joined in such a manner that the junction edges may not flushly match. Again, this may detract from the overall appearance of the instrument panel by reason of their being steps or gaps at the points of juncture. Further, the integrity of the connection of the door to the remainder of the instrument panel may not be as good as desired. Still further, the resin materials conventionally used for the instrument panel may not be desirable for use in making the door. Performance requirements for the door may be different than for the instrument panel. Again, this may compromise the appearance of the overall instrument panel.
To address the above problems associated with the separate door and instrument panel, different alternatives have been proposed whereby the external surface of the instrument panel is continuous and uninterrupted at the door region. Such an integral construction is shown in Japanese Unexamined Patent Application Publication No. 10-44910. This structure is shown in FIGS. 1 and 2 herein. More specifically, in those figures, an instrument panel is shown at 10. The instrument panel 10 has a layer 12 with a surface 14 that is exposed to a vehicle compartment 16. The layer 12 has a V-shaped groove 18 through an inside surface 20, facing oppositely to the surface 14, which groove 18 produces a frangible, reduced thickness portion 22 between an apex 24 of the groove 18 and the surface 14. The groove 18 extends continuously in a substantially rectangular pattern to define a xe2x80x9cdoorxe2x80x9d 26 for an airbag (not shown) that is deployed by expanding from the inside of the instrument panel 10 so as to project into the compartment 16.
The door 26 is rigidified by a reinforcing assembly at 28. The reinforcing assembly 28 consists of a reinforcing plate 30 which abuts to the back surface 32 of the door 26. The reinforcing plate 30 has a rearwardly bent flange 34 which is connected to one leg 36 of an L-shaped bracket 38. The other leg 40 of the bracket 38 is attached to a boss 42, fixed to and projecting rearwardly from, the layer 12. The leg 40 is connected to the boss 42 through a fastener 44. A threaded fastener 46 secures the bracket leg 36 to the flange 34. Separate threaded fasteners 48 extend through the reinforcing plate 30 and into the layer 12 to maintain the reinforcing plate 30 in place thereon.
The end 50 of the reinforcing plate 30, remote from the flange 34, is captive between the layer 12 and an L-shaped bracket 52. One leg 54 of the bracket 52 abuts to the flange end 50. The other leg 56 of the bracket 52 is secured by a fastener 58 against a boss 60, fixed to and projecting rearwardly from, the layer 12.
With the above construction, the door 26, with the reinforcing plate 30 attached thereto, is securely held in place so that the region around the door 26 is rigidified. With this arrangement, the expanding airbag repositions the door 26 without causing significant deformation or breakage of the remaining part of the instrument panel 10 around the door 26. However, to provide this reinforcement, it is necessary to separately form and attach the bosses 42, 60 on the back side of the layer 12 and to use a series of fasteners 44, 46, 48, 58 to maintain the overall integrity of the structure.
Another conventional airbag deployment system is shown in Japanese Unexamined Patent Application Publication No. 7-291078 and at 70 in FIG. 3 herein. The system 70 consists of an instrument panel 72 with a layer 74 having an exposed, outside surface 76 and an oppositely facing inside surface 78. A reinforcing plate 80 is secured against the inside surface 78 of the layer 74 and has a forward projection 82, which defines a reduced thickness, frangible portion 86 in the layer 74, which ruptures under the force of the expanding airbag 88, which is contained in a cup-shaped, forwardly opening, housing 90.
The reinforcing plate 80 has a series of openings 92 therethrough which accommodate heat deformable bosses 94 projecting rearwardly from the layer 74. The housing 90 has oppositely projecting flanges 96, 98 which are attached to the reinforcing plate 80 through bolts 100.
With this arrangement, a pivotable door 102 is defined. The door 102 itself is rigidified, as is the region of the instrument 72 therearound. Thus, the airbag 88 can be deployed without causing deformation or breakage of the instrument panel 72 around the door 102. At the same time, the outside surface 76 is not interrupted in the region of the door 102, so that a neat, continuous, external surface 76 is provided.
One potential difficulty with the system 70 relates to the selection of the size of the bosses 94. If the bosses 94 are too large, there may be shrinkage of the layer 74. To avoid this shrinkage problem, smaller bosses 94 may be utilized. However, at some point, the integrity of the bosses 94 may be compromised such that upon inflation of the airbag 88, the reinforcing plate 80 separates from the layer 74. The result of this may be damage to the region of the instrument panel 72 around the door 102.
In one form, the invention is directed to an airbag door assembly consisting of an instrument panel section, a reinforcing assembly, and a lining assembly. The instrument panel section has a core portion with an inside surface and an outside surface. An expanding airbag can project through the core portion of the instrument panel section. The reinforcing assembly is placed against the inside surface of the instrument panel section. At least part of the reinforcing assembly resides between the core portion and the lining assembly. The lining assembly and core portion are vibration joined at at least one location so as to maintain a part of the reinforcing assembly captively between the core portion and the lining assembly.
In one form, the core portion has a weakened portion that facilitates passage through the core portion of an expanding airbag, and the reinforcing assembly has a frame that extends around the weakened portion. The weakened portion may be frangible so as to rupture to facilitate passage of the expanding airbag through the core portion.
The reinforcing assembly may include a section that pivots in response to passage through the core portion of an expanding airbag.
In one form, one of the lining assembly and core portion has at least one part that passes through an opening in the frame assembly and is vibration joined to the other of the lining assembly and core portion.
In one form, the at least one part of the one of the lining assembly and core portion passes through a pivoting section on the reinforcing assembly.
In one form, the at least one part of the one of the lining assembly and core portion consists of a hollow post.
The hollow post may have a cylindrical shape with a peripheral wall with an inside surface surrounding an axis. The hollow post may further have a web spanning two locations on the inside surface of the peripheral wall and extending in a direction generally parallel to the axis of the hollow post.
In one form, an airbag associated with the airbag door assembly expands in a direction along a first line and the web extends generally parallel to the first line.
There may be a plurality of projections on one of the lining assembly and core portion that are vibration joined to the other of the lining assembly and core portion. Each of these projections may be hollow and/or cylindrical in shape.
In one form, the lining assembly and core portion are both made from the same material.
One or both of the lining assembly and core portion may be made from a thermal plastic olefin resin.
In one form, at least one of the projections has a free end with an effective diameter and the other of the lining assembly and core portion has a cavity into which the at least one projection extends. The cavity has an effective diameter that is larger than the effective diameter of the free end of the at least one projection.
In one form, the projection is hollow with an inside surface and an outside surface, with the inside surface diameter being at least 5 mm and the outside surface diameter being at least 20 mm. The inside surface diameter may be at least 10 mm, with the outside surface diameter being at least 30 mm.
The invention is also directed to an airbag door assembly having an instrument panel section and a reinforcing assembly. The instrument panel section has a core portion with an inside surface and an outside surface. An expanding airbag can project through the instrument panel section. A reinforcing assembly is placed on the inside surface of the instrument panel. The reinforcing assembly is maintained on the core portion by vibration joining an element to the core portion.
The element may be an element separate from the core portion and reinforcing assembly.
The invention is further directed to the combination of an airbag, having normal and expanded states, and an airbag door assembly, as previously described.
The invention is further directed to a method of making an airbag door assembly. The method includes the steps of: providing an instrument panel section having a core portion with an inside surface and an outside surface and through which an expanding airbag can project; placing a reinforcing element against the core portion; and through a vibration joining process, joining first and second elements so that the reinforcing element is maintained against the core portion.
The first element may be the core portion.
The second element may be a lining assembly that is initially separate from both the reinforcing element and the core portion.
In one form, the reinforcing element is captive between the core portion and the lining assembly.